High-Power Ultracapacitor Energy Storage Pack and Method of Use

ABSTRACT

In an energy storage cell pack including at least one energy storage cell that radiates heat in a longitudinal axial direction outwards, towards opposite electrically conductive and heat conductive terminals, a terminal heat sink includes a receiving section for structurally receiving a terminal of the opposite electrically conductive and heat conductive terminals, and more than one heat conductive cooling fin radiating outwardly from the receiving section, wherein the more than one cooling fin radiates outwardly from the terminal when the receiving section structurally receives the terminal for dissipating heat from the terminal to cool the at least one energy storage cell.

FIELD OF THE INVENTION

The field of the invention generally relates to an energy storagespecially adapted for a hybrid electric vehicle. In particular, theinvention relates to a high-voltage, high-power ultracapacitor energystorage pack composed of a large number of serially connected individuallow-voltage ultracapacitor cells that store propulsion energy.

BACKGROUND OF THE INVENTION

The connecting together of individual battery cells for high-voltage,high-energy applications is well known. However, the chemical reactionthat occurs internal to a battery during charging and dischargingtypically limits deep-cycle battery life to hundreds of charge/dischargecycles. This characteristic means that the battery pack has to bereplaced at a high cost one or more times during the life of ahybrid-electric or all-electric vehicle.

Batteries are somewhat power-limited because the chemical reactiontherein limits the rate at which batteries can accept energy duringcharging and supply energy during discharging. In a hybrid-electricvehicle application, the battery power limitation manifests itself as aninternal series resistance that restricts the drive system efficiency incapturing braking energy through regeneration and supplying power foracceleration.

Ultracapacitors are attractive because they can be connected together,similar to batteries, for high-voltage applications; have an extendedlife of hundreds of thousands of charge/discharge cycles; and have a lowequivalent internal series resistance that allows an ultracapacitor packto accept and supply much higher power than similar battery packs.Although ultracapacitor packs may be more expensive than battery packsfor the same applications and currently cannot store as much energy asbattery packs, ultracapacitor packs are projected to last the life ofthe vehicle and offer better fuel-efficient operation through brakingregeneration energy capture and supplying of vehicle acceleration power.Furthermore, the price of an ultracapacitor pack has the potential todecrease significantly because of economies of scale in knownmanufacturing techniques.

During charging and discharging operation of the ultracapacitors,parasitic effects, as modeled by the equivalent series resistance, causethe cell temperature to increase. Cooling is required to minimizeincreased temperature operation that would degrade the energy storageand useful life of each ultracapacitor.

Other than operation/performance, the key consideration forultracapacitor packs in a heavy duty hybrid-electric vehicle is heatdissipation. The ultracapacitor cells used in ultracapacitor packs areconstructed as layered sheets of conductive material and dielectric,wrapped around a central axis and forming a cylinder. Terminals areplaced on each end of the cell. The terminals are typically threaded andprovide both an electrical coupling point and a support point. Thethermal characteristics of this construction are such that most of heatgenerated by the cell is transferred to the environment via the two endsof the cell. Currently, heat dissipation is accomplished by blowingcooling air across the cylindrical bodies/cases of the cells.

Ultracapacitor packs in vehicles, especially heavy-duty vehicles, residein a harsh operating environment and face unique challenges not presentin non-vehicular applications. In particular, the vehicular environmentis dirty, hot, and subject to vibration. Current implementations attemptto address these problems, but leave room for improvement andinnovation.

In heavy-duty transit bus applications and other heavy duty vehicleapplications higher performance and smaller size ultracapacitor packsare required, especially where ultracapacitor packs are required to beplaced on the roof of the heavy-duty transit bus or other heavy dutyvehicle.

SUMMARY OF THE INVENTION

An aspect of the invention involves a terminal heat sink for use with aterminal of opposite electrically conductive and heat conductiveterminals of an energy storage cell of an energy storage cell pack. Theenergy storage cell radiates heat in a longitudinal axial directionoutwards, towards the opposite electrically conductive and heatconductive terminals. The terminal heat sink includes a receivingsection for structurally receiving a terminal of the oppositeelectrically conductive and heat conductive terminals and more than oneheat conductive cooling fin radiating outwardly from the receivingsection, wherein the more than one cooling fin radiates outwardly fromthe terminal when the receiving section structurally receives theterminal for dissipating heat from the terminal to cool the at least oneenergy storage cell.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthis specification, illustrate embodiments of the invention and togetherwith the description, serve to explain the principles of this invention.

FIG. 1 is a top plan and perspective views of an embodiment of anultracapacitor pack system.

FIG. 2 is an exploded perspective view of an embodiment of anultracapacitor energy storage cell pack of the ultracapacitor packsystem illustrated in FIG. 1.

FIG. 3 is an exploded perspective view of an embodiment of anultracapacitor pack assembly of the ultracapacitor energy storage cellpack of FIG. 2.

FIG. 4A is a perspective view of an upper cradle member of theultracapacitor pack assembly of FIG. 3.

FIG. 4B is a perspective view of a lower cradle member of theultracapacitor pack assembly of FIG. 3.

FIG. 5 is a perspective view of an alternative embodiment of anultracapacitor pack assembly.

FIG. 6A is a perspective view of the ultracapacitor pack assembly ofFIG. 3 after a first step in a method of assembly of the ultracapacitorpack assembly.

FIG. 6B is a perspective view of the ultracapacitor pack assembly ofFIG. 3 after a second step in a method of assembly of the ultracapacitorpack assembly.

FIG. 6C is a perspective view of the ultracapacitor pack assembly ofFIG. 3 after a third step in a method of assembly of the ultracapacitorpack assembly.

FIG. 6D is a perspective view of the ultracapacitor pack assembly ofFIG. 3 after a fourth step in a method of assembly of the ultracapacitorpack assembly.

FIG. 7 is a perspective view of an alternative embodiment of anultracapacitor pack assembly.

FIG. 8A is a perspective view of a further embodiment of anultracapacitor pack assembly.

FIG. 8B is a perspective view of an ultracapacitor and an embodiment ofultracapacitor holders for spacing and securing the ultracapacitors inthe ultracapacitor pack assembly of FIG. 8A.

FIG. 9A is a top perspective view of a still further embodiment of anultracapacitor pack assembly.

FIG. 9B is a bottom perspective view of the ultracapacitor pack assemblyof FIG. 9A.

FIG. 10 is a perspective view of an embodiment of terminal heat sinksand an interconnect for a pair of ultracapacitors.

FIG. 11A is a side elevational view of another embodiment of a terminalheat sink being applied to an ultracapacitor.

FIG. 11B is a top plan view of the terminal heat sink of FIG. 11A.

FIG. 11C is a side elevational view of the terminal heat sink of FIG.11A shown applied to the ultracapacitor.

FIG. 12 is a cross sectional view of an embodiment of an ultracapacitorpack cooling system of the ultracapacitor energy storage cell pack ofFIG. 2.

FIG. 13 is a perspective view of an alternative embodiment of anultracapacitor energy storage.

FIG. 14 is schematic view of an ultracapacitor and shows how theultracapacitor is supported in an embodiment of the cradle assembly ofthe ultracapacitor pack assembly.

DETAILED DESCRIPTION OF THE INVENTION

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

With reference to FIG. 1, an ultracapacitor energy storage system 100constructed in accordance with an embodiment of the invention will bedescribed. The ultracapacitor energy storage system 100 includes aplurality of ultracapacitor energy storage cell packs 110 connected to acentral water chiller 120 or cooling supply for cooling ultracapacitorsof the ultracapacitor energy storage cell packs 110, and a controller130 for controlling cooling of the ultracapacitor energy storage cellpacks 110 and/or controlling electrical functions (and/or otherfunctions) of the ultracapacitor energy storage cell packs 110. Asillustrated in this particular embodiment, each ultracapacitor energystorage cell pack 110 here includes 48 (6×8) ultracapacitors oriented sothat the longitudinal axis of each ultracapacitor is verticallyoriented. This configuration, along with the compact nature of eachultracapacitor energy storage cell pack 110, provides for low profile,modular ultracapacitor energy storage cell packs 110 that can bearranged in a variety of different configurations and numbers to providethe desired energy storage for the particular application. For example,FIG. 1 shows an exemplary configuration of six ultracapacitor energystorage cell packs 110 for assembly onto a rooftop of a metropolitantransit bus for supplying power to propel the bus. In otherapplications, different configurations, arrangements/orientations,and/or numbers of ultracapacitor energy storage cell packs 110 may beprovided. In alternative embodiments, the inventive principles describedherein are applied to batteries in a battery pack or other powersupplies in a power supply pack.

FIG. 2 is an exploded perspective view of an embodiment of theultracapacitor energy storage cell pack 110 of the ultracapacitor energystorage system 100 illustrated in FIG. 1. FIG. 3 is an explodedperspective view of an embodiment of an ultracapacitor pack assembly ofthe ultracapacitor energy storage cell pack of FIG. 2, further explodingcradle assembly 160. Here, the exemplary ultracapacitor energy storagecell pack 110 includes an ultracapacitor energy storage cell packassembly 140 with 48 (6×8) ultracapacitors 150 secured in place relativeto each other, housed within, and protected by cradle assembly 160. Inthe embodiment shown, the ultracapacitors 150 are Maxwell-Boostcap®Ultracapacitors model BCAP3000, rated at 3000 Farads, 2.7 Volt operatingvoltage, >1 million duty cycles.

With reference to FIGS. 3 and 10, terminal heat sinks 170, which aredisposed outside of cradle assembly 160 for cooling the ultracapacitors150 in a manner to be described, are thermally connected to terminals240 extending from opposite ends 250, 260 of each ultracapacitor 150.Interconnects 270 form an electrical bridging device that electricallyconnects terminals 240 from adjacent ultracapacitors 150 (to connect theultracapacitors 150 in series).

Referring to FIG. 2, the ultracapacitor energy storage cell pack 110includes a housing 180 comprised of an upper cover 190 and a lower cover200. The housing 180 includes fastener mechanisms for fastening theupper cover 190 to the lower cover 200. On an interior of the covers190, 200 are structural supports for supporting the ultracapacitorenergy storage cell pack assembly 140 at attachment/mounting points onthe ultracapacitor energy storage cell pack assembly 140. Theattachment/mounting points may be selected such that the pack assembly140 is oriented in an advantageous orientation. Disposed within one endof the housing 180 is a blower and cooler assembly 210 with a cross flowfan/flow source 220 and a heat exchanger 230. Although not shown,circuitry may be electrically coupled to the terminals 240 in awell-known manner.

With reference to FIGS. 3, 4A, and 4B, the cradle assembly 160 of theultracapacitor pack assembly 140 will be described in more detail. Asillustrated, the cradle assembly 160 includes a vacuum-formed orpressure-formed plastic upper cradle member 280 and a matchingvacuum-formed plastic lower cradle member 290 that form respective upperand lower array support structures for holding the ultracapacitors 150by opposite end portions of the ultracapacitor cell bodies instead of bytheir terminals 240. In the embodiment shown, the cradle members 280,290 may be made of a nonconductive material such as FR59 plastic. Eachcradle member 280, 290 includes a peripheral flange 300 with spaced boltholes 310 therein. The flange 300 surrounds a central recessed/raisedsection 320 (i.e. recessed on an inner surface 350/raised on an outersurface 360). Circular slots 330 are disposed in a wall/partition 340 ofeach cradle member 280, 290 to provide a terminal interface allowing theultracapacitor terminals to pass through. Each slot 330 includes arecessed annular wall 330 that projects outwardly from outer surface360. The annular wall 330 has a diameter slightly smaller than anexterior diameter of the ultracapacitor 150 for securably receiving(i.e., to provide spring force and/or grip on) the end portions 250, 260of the ultracapacitor 150. In certain applications, the cradle assembly160 may be further configured to direct air flow across the terminals.For example, the cradle assembly 160 may include vanes and/or formducting such that air/coolant does not bleed out of the desired flowpath, such that additional coolant is directed toward “hot spots” on thepack, such that back pressure on the flow source is reduced, etc.

One of the many advantages of the cradle assembly 160 is that it enablesthe ultracapacitors 150 to be placed closer together than was possiblein the past, making for a more compact ultracapacitor pack assembly 140.To this end, the slots 330 are disposed very close to one another. Anadditional advantage of disposing the slots 330 so close together isthat the annular walls 330 are disposed close enough together so thatthe plastic material that forms structural support for one annular wall330 adds to the structural support and rigidity of an adjacent annularwall 330. This increases the structural support provided by theslots/cups 330, increasing the structural support of the cradle assembly160 (i.e., the plastic material forming the annular walls 330 doubles inon itself to form the additional structural support.

The annular wall 330 terminates at a proximal end in the wall/partition340 and terminates at a distal end in annular flange 380. Annular flange380 extends radially inwardly from the annular wall 330 and includes acentral hole 390 with a diameter larger than an outer diameter of theterminal 240 (so the terminal 240 can pass there through) and smallerthan the outer diameter of the ultracapacitor 150 so that the endportions 250, 260 of the ultracapacitor 150 abut the annular flange 380while the terminal 240 passes through the hole 390. Thus, the circularslots 330 form cups for securably receiving end portions 250, 260 of theultracapacitors 150.

Preferably the ultracapacitors 150 are oriented along the dominant axisof vibration (See FIG. 14), which is typically vertically, as shown, forvehicle applications. The ultracapacitors 150 are supported by theircylindrical body/case 434 and end portions/caps 250, 260 rather than bytheir terminals 240.

With reference to FIG. 5, an alternative embodiment of a cradle assembly400 is shown. The cradle assembly 400 is similar to the cradle assembly160 described above except that the cradle assembly 400 includes legstands 410 for supporting the cradle assembly 400 in the housing 180. Infurther embodiments, the cradle assembly 160, 400 includes additional orfewer features, such as, but not by way of limitation added stiffeningribs (e.g., integrally formed with the cradle members 280, 290) orseparate stiffeners (not shown) added between rows/columns ofultracapacitors 150 to add structure in the cradle members 280, 290 or asmaller flange 300 (or no flange 300).

In an alternative embodiment, the ultracapacitors 150 are laterallysupported or slid into a middle support structure between the cradlemembers 280, 290 (or other top/bottom support plates/structures). Themiddle support structure may be used for fire suppression, stress relieffor the cradle assembly, vibration dampening, additional structure,and/or stability.

With reference to FIGS. 2, 6A-6D, and 10, an exemplary method ofassembly of the ultracapacitor pack assembly 140 will be described.First, with reference to FIG. 6A, the ultracapacitors 150 are assembledinto the slots/cups 330 of the lower cradle member 290 so that lower endportions 260 of the ultracapacitors 150 rest on the annular flange 380while the terminals 240 pass through the holes 390. Second, the uppercradle member 280 is assembled onto the ultracapacitors 150 so that topend portions 250 of the ultracapacitors 150 rest on the annular flange380 while the terminals 240 pass through the holes 390 (i.e., top endportions 250 are assembled into the slots/cups 330). Third, theinterconnects 270 are assembled so as to electrically connect terminals240 from adjacent ultracapacitors 150 (to connect the ultracapacitors150 in series). Fourth, the terminal heat sinks 170 are fastened to theterminals 240. Fasteners (e.g., bolts/nuts) are used to connect theflanges 300 of the cradle members 280, 290 together and theultracapacitor pack assembly 140 is inserted into the lower cover 200.The cradle members 280, 290 generally enclose and protect theultracapacitors 150 so that the ultracapacitor pack assembly 140 forms amodule. The ultracapacitor pack assembly 140 may be supported in theultracapacitor energy storage cell pack 110 by the flanges 300. Theother components and/or circuitry of the ultracapacitor energy storagecell pack 110 may be installed into the lower cover 200 before, during,or after the ultracapacitor pack assembly 140 is assembled and insertedinto the ultracapacitor energy storage cell pack 110.

The ultracapacitor pack assembly 140 is advantageous because it isquick, easy, and inexpensive to assemble/manufacture, includes fewercomponents that ultracapacitor pack assemblies in the past, relieves theterminals 240 from supporting the ultracapacitors 150, is vibrationresistant, forms a streamlined, compact ultracapacitor pack assembly,offers excellent high voltage isolation protection, provides robustenvironmental protection of components, particularly the ultracapacitors150, for heavy duty applications, and provides excellent thermalinsulation to reduce system heat rejection requirements. Its modularitygives vehicle manufacturers and integrators flexibility in configuringthe energy storage on the vehicle. In addition, it provides for asingle, uniform module that can be used in varying numbers to meetdiverse energy storage requirements.

As illustrated in FIG. 14, the ultracapacitors 150 aredisposed/supported with their longitudinal axis vertically oriented. Endportions 250, 260 and body 434 of the ultracapacitors 150, as opposed tothe terminals 240, are structurally supported in the slots 330 of thecradle members 280, 290, protecting the structural integrity of theultracapacitors 150 and preventing damage to the terminals 240 or damageto the ultracapacitors 150 from being structurally supported by theterminals 240. Vibration during vehicle travel is often in a vertical(up and down) direction as shown. Structurally supporting the endportions 250, 260 and the body 434 of the ultracapacitors 150, with theultracapacitors 150 vertically oriented as shown, protects thestructural integrity of the ultracapacitors 150 during vibration of theultracapacitor pack assembly 140 and vehicle. The cradle members 280,290 combine to form a protective, sealed, enclosed housing/cover/box forthe ultracapacitors 150, protecting the ultracapacitors 150 from dirt,dust, debris, water, and other contamination.

With reference to FIG. 7, an alternative embodiment of an ultracapacitorpack assembly 420 will be described. Similar to cradle assembly 160, theultracapacitors 150 are supported by the opposing end portions 250, 260of their casings, however, rather than wrapping down the sides of thearray of ultracapacitors 150 and coupling to each other, the supportingmembers are kept apart and do not generally enclose the ultracapacitors150. Instead, the upper and lower supporting members are coupled to eachother via an intermediate member. In this way access is provided to thecenter area of the ultracapacitors 150 between their terminals 240. Thismay be beneficial for routing electronic circuitry (e.g., monitoring,balancing, and protection circuitry). Also, this may provide asupplemental cooling path to cool the ultracapacitor bodies 434 inaddition to their terminals 240. For example, as illustrated in FIG. 7,the ultracapacitor pack assembly 420 includes an upper support board(e.g., FR4 board) 430 and a lower support board 440 with holes thereinto receive end portions of ultracapacitors 150. As above, theultracapacitors 150 are oriented along the dominant axis of vibration(See FIG. 14), which is typically vertically, as shown, for vehicleapplications. Similarly, the ultracapacitors 150 are supported by theircylindrical body/case 434 rather than by their terminals 240. Verticalsupport members/posts 450 couple and support the support boards 430, 440and rest of the ultracapacitor pack assembly 420 with reference to eachother and to the housing 180. Plastic brackets 460 are inexpensivelydisposed on outer surfaces of the support boards 430, 440 for retainingthe end portions of the ultracapacitors 150 in the Z-direction relativeto the support boards 430, 440. Plastic blind rivets/plastic splitshanks 470 are used to fasten the plastic brackets 460 to the supports430, 440 via holes in the support boards 430, 440. It is understood thatother means may be used to secure the ultracapacitor in the verticaldirection. For example, upper and lower support boards may integrate acup interface to receive and restrain the end portions 250, 260 ofultracapacitor 150. Likewise a ring section of a second board may beattached to support boards 430, 440 wherein its inner diameter is largerthan the terminal but smaller than the end portion of the ultracapacitorcell, and the diameter of boards 430, 440 are approximately the same asthat of the cell.

With reference to FIGS. 8A and 8B, a further embodiment of anultracapacitor pack assembly 471 will be described. Here, a differentapproach is taken. Ultracapacitors 150 are equipped with adaptors orholders that transfer support loading to their end portions 250, 260. Inaddition, the adaptors/holders 475 extend the interface with theultracapacitor to provide a flow path for a coolant to convect heat. Forexample, as illustrated, the ultracapacitor pack assembly 471 includesan upper support plate (e.g., ABS/PVC plate) 472 and a lower supportplate 473 with sets of support holes or slots on inner surfaces of theplates 472, 473 to receive spacer supports or support pegs 474 (FIG. 8B)of ultracapacitor holders 475. As above, the ultracapacitors 150 arepreferably oriented along the dominant axis of vibration (See FIG. 14),which is typically vertically, as shown, for vehicle applications.Vertical support posts 476 couple and support the support plates 472,473 and rest of the ultracapacitor pack assembly 471.

The ultracapacitor holders 475 function as extension devices, one foreach end of the ultracapacitor 150. Moreover, the ultracapacitors 150are supported by their cylindrical body/case 434 rather than by theirterminals 240. As illustrated, the ultracapacitor holders 475 includeannular cuffs 477 that are akin to cup holders and slidably receive endportions of the ultracapacitors 150. The support pegs 474 extend fromthe annular cuff 477 and are circumferentially spaced along the annularcuff 477. When assembled as shown in FIG. 8A, the ultracapacitor holders475 perform the following functions: (1) space the ends of theultracapacitors 150 from the inner surfaces of the support plates 472,473; (2) provide a passage for coolant (e.g., cooled air flow) to passover the terminal heat sinks 170 for cooling the ultracapacitors 150;and (3) provide an interface with the support plates 472, 473.

Preferably, the ultracapacitor holders 475 and the support plates 472,473 are interfaced so that the ultracapacitor holders 475 can notrotate, translate, or pass through the support plates 472, 473. In thisway coolant flow can be better controlled in a predictably way. Once theultracapacitors 150 are positioned, the support plates 472, 473 arefastened together, thus holding the ultracapacitors 150 by theircylindrical bodies/cases 434 only. The unified structure can then besupported by a housing of the ultracapacitor pack assembly 471. Thisembodiment lends itself well to low cost mass production wherein theuniform end holders are placed on both ends of the ultracapacitors 150and inserted into machined slots in the support plates. Preferably, themachined slots are keyed such that the resultant flow path is made in anoptimal predetermined manner.

With reference to FIGS. 9A and 9B, a still further embodiment of anultracapacitor pack assembly 500 will be described. Here, theultracapacitor casings are supported both laterally and at their endportions, For example, as illustrated, the ultracapacitor pack assembly500 includes a support matrix 510 (e.g., a foam or polymer core) withcylindrical holes therein having a diameter similar to the externaldiameter of the ultracapacitors 150 for slidably receiving/supportingthe ultracapacitors 150 therein. In addition, the support matrix 510 mayhave plastic dividers or other support members disposed therein (e.g.,elongated, thin plastic support dividers disposed between rows and/orcolumns of ultracapacitors 150) for adding structural support to thefoam core support matrix 510 for example. Preferably, theultracapacitors 150 are oriented along the dominant axis of vibration(See FIG. 14), which is typically vertically, as shown, for vehicleapplications.

The ultracapacitors 150 are supported by their cylindrical body/case 434rather than by their terminals 240. In particular, the ultracapacitors150 may be held in position by friction force applied to the externalsurface/sides of the cylindrical body/case 434. For example, wheremultiple ultracapacitors 150 are supported, the ultracapacitors 150 maybe held by a pressure-fit within a supporting structure (e.g., a foamcore support matrix 510, a grid support structure having a frictioninterface (not shown), etc.). In the embodiment shown, the cylindricalholes of the support matrix 510 are slightly smaller than the externaldiameter of the ultracapacitors 150; the ultracapacitors 150 may besupported primarily laterally by their casings.

Alternately, the ultracapacitors 150 may be positioned and held in placeby injecting foam (or other setting material) between theultracapacitors 150 and a supporting structure. Preferably, the multipleultracapacitors 150 are positioned in a structural grid, and then thefiller material is applied. In this way, individual ultracapacitors 150may be removed without disturbing the balance of the array. In analternative embodiment, the structural grid may be supported by ahousing of the entire energy storage pack. Alternately, when using thestructural grid, the filler material may be a non-expanding frictionmaterial (e.g., rubber, epoxy, etc.) that is fixed to the grid and holdsthe canister in place.

Alternately, where the diameter of the cylindrical holes of the supportmatrix 510 are slightly larger than the external diameter of theultracapacitors 150, the ultracapacitors 150 may be supported primarilyby their end portions via end brackets fixed to the support matrix 510.For example, as illustrated and similar to FIG. 7 discussed above,plastic end brackets 530 are fastened on the lower surface of the foamcore support matrix 510 for retaining the end portions of theultracapacitors 150 in the Z direction relative to the support matrix510.

In this and the abovementioned embodiments, support matrix 510, thefiller material, and/or the grid are preferably made from a flameresistant material. Similarly, here and above, vertical support posts520 may be used to support the support matrix 510 within the rest of theultracapacitor pack assembly 500.

With reference to FIG. 10, the interconnects 270 and the terminal heatsinks 170 will now be described in greater detail in turn below. Eachinterconnect 270 forms a conductive path between the terminals 240 oftwo ultracapacitor cells 150. In this way multiple cells can beelectrically coupled in series, thus aggregating the total voltage ofthe cell to a level suitable for hybrid-electric propulsionapplications. For example, as illustrated here interconnect 270 may bemade from a solid stamped piece of aluminum including a pair of flatterminal receivers 540 with holes 542 therein to receive the terminals240 of the ultracapacitors 150. Additionally, interconnect 270 mayinclude an access point for cell control and monitoring. In particular,extending upward from the flat bridge section 554 is a terminal 560(e.g., for connecting monitoring or control circuitry such as balancingresistor(s), control circuit, etc.). Being primarily an electricalbridging device, it is preferable that interconnect 270 be sufficientlyflexible so as not to induce stresses in the terminals in excess of itstolerance upon installation. For example, the flat terminal receivers540 include a bridge 550, which may be flexible (e.g., thinner materialused in bridge 550 and/or multiple preformed bends may be used to makethis section flexible), having opposite upwardly angled sections 552extending upwardly and inwardly from the flat terminal receivers 540.The opposite upwardly angled sections 552 are joined by a flat bridgesection 554.

Each terminal heat sink 170 forms a thermally conductive path away fromthe terminal 240 of ultracapacitor cell 150 that it is mechanicallycoupled to. In particular, terminal heat sink 170 axially transfers heatmore efficiently through the ultracapacitor terminals, instead ofradially across the internal dielectric layers and through the canisterwalls. Further terminal heat sink 170 may include a heat exchangerhaving a thermal performance sufficiently high that the terminal heatsink 170 provides at least half of the required cooling of theultracapacitor cell 150. Preferably, terminal heat sink 170 will be madeof a material similar to that of the cell terminals. For example, sinceultracapacitor terminals are often made of aluminum, terminal heat sink170 could also be made of aluminum. There are several benefits of usingthe terminal heat sink 170 as disclosed herein. For example, while someheat exchange takes place via interconnect 270, the incorporation ofcooling surfaces (e.g., fins) would tend to stiffen the interconnect andinduce stress in the terminals. In addition, the omnidirectionalorientation of terminal heat sink 170, as illustrated, provides for asingle component/device for use on each cell, independent of the cell'sorientation in the series string and further provides for simpleinstallation.

The thermal performance required of terminal heat sink 170 will varyaccording to each application. In particular, it may vary depending onparameters such as the performance desired of the cell, the convectionmode and media, the flow rate of the convection media, the thermalgradient between the cell and coolant, etc. Once the parameters areknown, the systemic heat transfer coefficient and terminal heat sinkthermal performance may be determined as a result of a standardcomputational fluid dynamics (CFD) analysis. By cooling axially at theterminals, the cells may be cooled much more efficiently and/or thecells may have higher performance, making the energy storage bettersuited for hybrid-electric propulsion applications.

As illustrated in FIG. 10, the terminal heat sink 170 forms an energystorage cell terminal cooler/exchanger, or a device that radiates heatfrom an individual terminal 240. The terminal heat sink 170 couples tothe terminal 240 and provides a heat exchange surface to the surroundingenvironment. In the embodiment shown, the cooling fins 580 form aconvective heat exchange surface in an air flow path. The heat exchangesurface may be integrated into a fastener for the terminal 240 (e.g., athreaded nut 570). Accordingly, the terminal heat sink 170 may bothcouple items to the ultracapacitor 150 terminal as needed and cool theterminal end of the ultracapacitor 150 at the same time. In anotherembodiment, the terminal heat sink 170 is configured to bolt a busbar(or other terminal-to-terminal interconnector/electrical bridgingdevice) to the ultracapacitor 150. According to another embodiment, theterminal heat sink 170 may be configured to provide lateral support(i.e., along the longitudinal axis of the ultracapacitor 150) so as tosupport the ultracapacitor 150 within a housing or enclosure. Byproviding more efficient cooling and moving the heat exchange locationaway from the canister walls, the terminal heat sinks 170 enable theultracapacitors 150 to be packed more closely to each other so thatcooling air is primarily passed across the terminal ends. By doing so,there is less need for a large cooling air/heat exchange path betweenthe ultracapacitors 150.

According to one exemplary construction, and as illustrated in FIG. 10,each terminal heat sink 170 includes a nut 570 with a threaded interiorfor threadably receiving externally threaded terminal 240 (see also,FIG. 11C ref. 620). The nut 570 is welded to a cylindrical tube (notshown). The nut 570 and/or the tube form a receiving section forstructurally receiving externally threaded terminal 240. Annular washersor cooling fins 580 circumferentially surround and extend radially fromthe cylindrical tube. A top of the terminal heat sinks 170 may include arotate engagement mechanism/recessed tool interface 590 for rotatableengagement by/with a rotatable tool for screwing the terminal heat sink170 on/off the externally threaded terminal 240. In the embodimentshown, the rotate engagement mechanism 590 includes a “key” interface;particularly, three geometrically spaced cylindrical female sections(e.g. bores) for receiving three corresponding male members of arotatable tool for screwing the terminal heat sink 170 on/off theexternally threaded terminal 240. Thus a key is required to remove theterminal heat sink 170, providing added security against unauthorizeddisassembly. In alternative embodiments, the rotate engagement mechanism590 may include other configurations/structures (e.g., screwdriver slot,Allen stock recess) for rotatable engagement by/with a rotatable tool.The rotate engagement mechanism 590 is also important for controllingthe amount of torque applied to the threaded terminal 240 so that theterminals 240 and ultracapacitors 150 are not damaged by applying toomuch torque. The rotate engagement mechanism 590 is preferably recessedin the top/exposed end of the terminal heat sink 170 since it ispreferable that whatever rotatable tool is used to screw/unscrew theterminal heat sink 170 comes in from the top/exposed portion of thethreaded terminals 240.

With reference to FIG. 11A-11C, an alternative construction of aterminal heat sink 610 will be described. The terminal heat sink 610 isgenerally similar to the terminal heat sink 170 described above exceptthat the terminal heat sink 610 includes an interiorly threaded nut 620disposed above the cooling fins 580 instead of below the cooling fins580 as with the heat sink 170 of FIG. 10. Annular washers or coolingfins 580 circumferentially surround and extend radially from cylindricaltube 630. Cylindrical tube 630 may be smooth or internally threaded. Inthe terminal heat sink 610, the nut 620 is a standard hexagonal nut. Thestandard hexagonal outer surface of the nut 620 forms a rotateengagement mechanism for rotatable engagement by/with a rotatable tool(e.g., wrench) for screwing the terminal heat sink 610 on/off theexternally threaded terminal 240.

As shown in FIG. 11C and discussed above, heat radiates in alongitudinal axial direction outwards, towards the terminals 240, in thedirection of the arrows shown. The heat is transferred to the terminals240, and from the terminals 240, through the nut 620/tube 630 and to thecooling fins 580. Convective cooling air flows past the cooling fins 580to transfer heat therefrom to cool the ultracapacitor 150.

According to one exemplary construction, the terminal heat sink 610 maybe simply, quickly, and easily manufactured by sliding L-type annularwasher(s) 580 along the outside of the tube 630 into desired positionsand enlarging the outer diameter of the tube 630 relative to an innerdiameter of annular L-type washers (e.g., by forcing a ball bearinghaving a larger diameter than an inner diameter of the tube 630 throughthe tube 630) so that the washers are fixed to the tube 630.Alternatively, the washer(s) 580 may then be welded (or otherwise fixed)to the end of the tube 630. Alternatively, terminal heat sink 610 ismanufactured by sliding L-type annular washers along the outside of thetube 630 into desired positions and fixing the inner annular portion ofannular L-type washers to the outer circumference of the tube 630 andfixing the nut 620 to end of the tube 630. Fixing the componentstogether may be performed by brazing, welding, and/or other fixingtechniques.

In alternative embodiments of the terminal heat sink 170, 610, thenumber and/or configuration(s) of the heat fins 580 may vary/differ fromthat shown. For example, but not by way of limitation, in one or moreembodiments, terminal heat sink 170, 610 includes one or more of thefollowing features, the terminal heat sink 170, 610 radiates outwardlyin a symmetric configuration from the receiving section, the symmetricconfiguration is annular, and/or the symmetric configuration is at leastone of curvilinear (e.g., circular, annular, oval) and rectilinear(e.g., square, rectangular, rhomboid, parallelogram). However the finsare preferably circular, in this way the terminal heat sink 170, 610provides omnidirectional cooling and may be installed in any direction,thus making installation quicker. Also, the dimensions of the heat fins580 are preferably less than the diameter/dimensions of theultracapacitors 150. For example, but not by way of limitation, theouter diameter of the heat fins 580 is less than the outer diameter ofthe ultracapacitor 150. This minimizes the separation of adjacent cellsand interaction between adjacent terminal heat sinks 170, 610.Additionally, the first fin (closest to the ultracapacitor 150 end maybe in direct contact with the end of the cell for increased heattransfer, or alternately may stand off the end of the cell for increasedcoolant flow and convection.

The terminal heat sink 170, 610 is advantageous because, but not by wayof limitation, it extracts heat from the ultracapacitor cell in athermally efficient manner and without the need for a high flow coolingsystem. The terminal heat sink 170, 610 provides a low-cost, simplesolution for transferring heat from the ultracapacitors 150. Theterminal heat sink 170, 610 provides cooling for individualultracapacitors 150, and provides maximum cooling at the points (i.e.,terminal ends) of highest heat. The terminal heat sink 170, 610 alsoallows for a more compact form factor in the ultracapacitor packassembly because the ultracapacitors 150 can be placed closer togethersince cooling occurs at the terminals 240 and not at the cylindricalbody/case 434. Similarly, since the cells are cooled more efficiently,less cooling air is required and consequently much less energy isrequired to perform the same cooling.

With reference to FIG. 12, an embodiment of ultracapacitor pack coolingsystem 650 for the ultracapacitor energy storage cell pack 140 will bedescribed. Preferably, ultracapacitor pack cooling system 650 is aclosed loop system. In this way, external contaminates commonly found inhybrid vehicles are excluded from the energy storage, thus extending itslife and reliability. The ultracapacitor pack cooling system 650includes the blower and cooler assembly 210 disposed within one end ofthe housing 180. The blower and cooler assembly 210 includes the crossflow fan/flow source 220 and the heat exchanger 230. The cross flowfan/flow source 220 and the heat exchanger 230 are laterally elongatedand extend substantially the entire lateral length of the ultracapacitorenergy storage cell pack 140. In other words, the width of the crossflow fan/flow source 220 and the heat exchanger 230 is substantially thesame width of each row (e.g., 6 rows shown in embodiment of FIG. 2). Ofcourse, cross flow fan/flow source 220 may be a fan extending the lengthof first row 692 of ultracapacitors 150, or it may include thecombination of a smaller fan and ducting or vanes distributing the flowto first row 692 of ultracapacitors 150. Preferably, a, front portion ofthe cross flow fan/flow source 220 includes upper guide 660 and lowerguide 670 that form a shroud for directing air flow from the cross flowfan/flow source 220 in the manner shown in FIG. 12 and minimizesleakage.

Coolant flow or a coolant flow path 680 flows over and through the upperterminal heat sinks 170, causing convective cooling of the cooling fins580 (transferring heat from the upper terminals 240) to cool theultracapacitors 150. Air flows around an opposite end of theultracapacitor energy storage cell pack 140 and back to the heatexchanger 230 via a return flow or return flow path 690. Similar to theconvective cooling that occurs in the coolant flow path 680, the returnflow 690 flows over and through the lower terminal heat sinks 170,causing convective cooling of the cooling fins 580 (transferring heatfrom the lower terminals 240) to cool the ultracapacitors 150.Generally, air flow will be substantially or completely blocked fromcrossing/bleeding over the side of the ultracapacitor energy storagecell pack 140. This may be accomplished with dedicatedducting/blockage/sealants and/or configuring structures such as thehousing 180 or cradle assembly 160 to perform this task

According to the illustrated embodiment, the temperature of the returnflow 690 is higher than the temperature of the coolant flow path 680because the return flow 690 includes the heat removed from upstream flowacross the terminal heat sinks 170. Thus, the temperature gradientassociated with the air flow above the first row 692 of ultracapacitors150 is the highest and the temperature gradient associated with the airflow below the first row 692 of ultracapacitors 150 is the lowest.Since, heat transfer occurs in a longitudinal axial direction outwards,towards the terminals 240, in the direction of the arrows shown in FIG.11C, and in light of the varying temperature gradients, the first row ofcells may experience greater cooling at the top terminal than at thebottom terminal, whereas the last row of cells may experience a moreeven cooling at the top and bottom terminals. However, the averagetemperature of the air flow above and below each row of ultracapacitors150 is the same for every row (i.e., every row has the same averagetemperature). As a result, each row of ultracapacitors 150 (as well asall ultracapacitors 150) are cooled the same.

The heat exchanger 230 removes the added heat from the return flow 690from the energy storage cell pack 110. Heat exchanger 230 may utilize anexternal cooling supply as well. For example, preferably heat exchanger230 will be integrated in a vehicle cooling system. In particular, acoolant will pass through the energy storage cell pack 110 extractingheat from the hotter air flow. This may be accomplished by passing thecoolant through a finned tube and passing the heated air flow across it.With reference additionally to FIG. 1, the heat exchanger 230 from eachultracapacitor energy storage cell pack 110 may be connected to acentral water chiller or cooling supply 120 for transferring coolantthrough the heat exchangers 230 for removing heat from theultracapacitor energy storage cell packs 110. The flowing coolant takesheat from the ultracapacitors 150, and the heat in the coolant isremoved with the heat exchanger 230. The controller 130 may controlcooling of the ultracapacitor energy storage cell packs 110 measuringthe temperature of the packs and metering the coolant flow and/ortemperature. Additionally, the heat exchanger 230 may be locatedexternal to the housing; however the cooling air of the pack ispreferably part of a closed-loop system.

According to the preferred embodiment shown, both the cross flowfan/flow source 220 and the heat exchanger 230 are integrated into theultracapacitor energy storage cell pack 110. Preferably, the heatexchanger 230 is cooled externally using coolant from either the vehiclecooling system (not shown) or a central water chiller or cooling supply120 (FIG. 1). In an alternative embodiment, one or both of the crossflow fan/flow source 220 the heat exchanger 230 are not integrated intothe ultracapacitor energy storage cell pack 110.

According to the embodiment shown, the ultracapacitors 150 arevertically arranged in a single-level array, and the coolant (e.g., air)will pass over the top (and/or or bottom) of the ultracapacitors 150,wrap around, and enter the heat exchanger 230 to extract heat. Theterminal heat sinks 170 on the terminals 240 form mini heat exchangers(e.g., finned nuts) so as to improve the transfer of heat from theterminals 240 to the coolant. This design is particularly good withultracapacitors 150 because the internal construction of theultracapacitors 150 makes it far more efficient to extract heat from theterminals 240 rather than the cases/cylindrical body 434 of theultracapacitors 150. This is true even though there is much more surfacearea around the external surface of the cases/cylindrical body 434 thanthe external surface of the terminal 240, making this cooling approachcounterintuitive, especially since one would think that enclosing thehot ultracapacitors 150 in a sealed, enclosed box would raise thetemperature of the ultracapacitors 150. As shown in FIG. 11C, heatradiates in a longitudinal axial direction outwards, towards theterminals 240, in the direction of the arrows shown. The heat istransferred to the terminals 240, and from the terminals 240, throughthe tube 630 and to the cooling fins 580. According to one embodiment,as shown in FIG. 12, the cooling air is propelled by cross flow fan 220in a linear, uniform flow across the terminal heat sinks 170. This crossflow fan (also called a tangential flow fan) provides for uniform andpredictable heat transfer. As illustrated, the cross flow fan 220efficiently redirects the air flow from the integrated heat exchanger230 back over the terminal heat sinks 170, thus closing theultracapacitor cooling loop. The cross flow fan 220 spans the longprofiles associated with the cell array in the most efficient manner(compared to, for example, axial fans and centrifugal fans, which mayrequire multiple motors and add bulk to the housing, based on theirprinciples of operation). The above closed-loop cooling strategy/systemprovides active cooling, allowing operation of the ultracapacitor packin all climates, and provides consistent cell-to-cell temperaturecontrol as compared to open loop systems that may vary depending onambient conditions.

As used in a hybrid electric vehicle, some of the characteristics of theultracapacitor energy storage cell pack 110 may include a rated voltageof 2.3×48=110.4 V, a recommended max voltage of 2.5×48=120 V, a surgevoltage of 2.7×48=129.6 V, an isolation voltage of 2500 V, a ratedcontinuous current of 150 A (peak of 300 A), a leakage current of <5 mA,a number of 48 cells (each rated at 3000 F) in the module, a lifetime of40000 hrs (based on a continuous 33 kW cycle), 1 million Cycles (50%DoD), capacitance of 62.5 F, total energy stored nominal of 105.8 Wh(2.3 V/cell), total energy stored peak of 125 Wh (2.5 V/cell), DC ESR of16.5 mOhms, heat rejection of 3 kW, cooling water of 30-35 degrees C. at10 gpm (plumbed in parallel), a storage temperature of −40 degrees C. to70 degrees C., an operating ambient temperature of −40 degrees C. to 50degrees C., and a vibration meeting SAE J2380 & J244, an IP rating ofIP67, an IEC rating of iec 529 (Type 5), a height dimension of no morethan 13 in., a length dimension of no more than 15 in., and a widthdimension of no more than 17 in., and a total dimension/volume that doesnot exceed 13 in.×15 in.×17 in. In addition, while there is no maximumlimit to the spacing between the ultracapacitors, preferably thereshould be no more that 0.25 in.-0.50 in. between the casings of thecells.

Some of the characteristics of the ultracapacitor pack system 100include a supply voltage of 230 VAC, a rated voltage of 110.4×6=662 V, arecommended max voltage of 120×6=720 V, a surge voltage of 129.6×6=777V, an isolation voltage of 2500 V, a rated continuous current of 150 A,a rated peak current of 300 A, a leakage current of <5 mA, a number ofmodules/ultracapacitor energy storage cell packs 110 of 6 modules in theultracapacitor pack system 100, a lifetime of 40000 hrs (based on acontinuous 33 kW cycle), 1 million Cycles (50% DoD), capacitance of 10.4F, total energy stored nominal of 634 Wh (2.3 V/cell), total energystored peak of 750 Wh (2.5 V/cell), DC ESR of 98 mOhms, heat rejectionof 3 kW (10236 BTU/hr), cooling water of 30-35 degrees C. at 10 gpm(0.758 L/s), a storage temperature of −40 degrees C. to 70 degrees C.,an operating ambient temperature of −40 degrees C. to 50 degrees C., amaximum ambient temperature range inlet of 60 degrees C., vibrationmeeting SAE J2380 & J244, 144 temperature sensors, an IP rating of IP67,an IEC rating of iec 529 (Type 5), a Beginning of Life (BOL) power lossof no more than 2251 W, and an End of Life (EOL) power loss of no morethan 2701 W.

The ultracapacitor pack system 100 preferably includes ground faultcircuit protection, a CAN vehicle interface, contactor protectionhardware/software, microprocessor controlled cell equalization andmonitoring, integral DC Bus precharge resistor(s), fast-acting fuse thatreduces damage to DC bus components in event of a short circuit,diagnostic and prognostic functions to predict faults before they occur,and a monitoring system that monitors the voltage and temperature ofevery capacitor 150 to eliminate hidden cell failures.

With reference to FIG. 13, an alternative embodiment of anultracapacitor energy storage cell pack 700 will be described. Theultracapacitor energy storage cell pack 700 is generally similar to theultracapacitor energy storage cell pack 110 of FIG. 2, except instead ofthe ultracapacitor energy storage cell pack 110 including a singleultracapacitor energy storage cell pack assembly 140, the ultracapacitorenergy storage cell pack 700 includes more than one (e.g., 3)ultracapacitor energy storage cell pack assembly 140 disposed inrespective inner thermoform liners 710 designed to readily receive allthe components (e.g., ultracapacitor pack assemblies 140) of theultracapacitor energy storage cell pack 700 for quick, inexpensive, andeasy assembly. A single elongated cross-flow fan 720 and a single heatexchanger 730 are used to cool the multiple ultracapacitor energystorage cell pack assemblies 140. The single elongated cross-flow fan720, the single heat exchanger 730, and the multiple ultracapacitorenergy storage cell pack assemblies 140/inner thermoform liners 710 aredisposed within a housing including a lower cover or sheet metal casing750 and an upper cover or top 760. The single heat exchanger may supplyits own cooling or may be connected to a central water chiller orcooling supply 120 as described above for transferring coolant throughheat exchanger(s) 730 for removing heat from one or more ultracapacitorenergy storage cell packs 700.

The above figures may depict exemplary configurations for the invention,which is done to aid in understanding the features and functionalitythat can be included in the invention. The invention is not restrictedto the illustrated architectures or configurations, but can beimplemented using a variety of alternative architectures andconfigurations. Additionally, although the invention is described abovein terms of various exemplary embodiments and implementations, it shouldbe understood that the various features and functionality described inone or more of the individual embodiments with which they are described,but instead can be applied, alone or in some combination, to one or moreof the other embodiments of the invention, whether or not suchembodiments are described and whether or not such features are presentedas being a part of a described embodiment. Thus the breadth and scope ofthe present invention, especially in the following claims, should not belimited by any of the above-described exemplary embodiments.

Terms and phrases used in this document, and variations thereof, unlessotherwise expressly stated, should be construed as open ended as opposedto limiting. As examples of the foregoing: the term “including” shouldbe read as mean “including, without limitation” or the like; the term“example” is used to provide exemplary instances of the item indiscussion, not an exhaustive or limiting list thereof; and adjectivessuch as “conventional,” “traditional,” “standard,” “known” and terms ofsimilar meaning should not be construed as limiting the item describedto a given time period or to an item available as of a given time, butinstead should be read to encompass conventional, traditional, normal,or standard technologies that may be available or known now or at anytime in the future. Likewise, a group of items linked with theconjunction “and” should not be read as requiring that each and everyone of those items be present in the grouping, but rather should be readas “and/or” unless expressly stated otherwise. Similarly, a group ofitems linked with the conjunction “or” should not be read as requiringmutual exclusivity among that group, but rather should also be read as“and/or” unless expressly stated otherwise. Furthermore, although item,elements or components of the disclosure may be described or claimed inthe singular, the plural is contemplated to be within the scope thereofunless limitation to the singular is explicitly stated. The presence ofbroadening words and phrases such as “one or more,” “at least,” “but notlimited to” or other like phrases in some instances shall not be read tomean that the narrower case is intended or required in instances wheresuch broadening phrases may be absent.

1. A device for cooling an energy storage cell in a hybrid electricvehicle, the energy storage cell having a first terminal, the devicecomprising: a terminal interface configured to mechanically andthermally couple the device to the first terminal; and, a heat exchangerradiating outwardly from the first terminal and configured toconvectively transfer heat away from the first terminal.
 2. The deviceof claim 1, wherein the terminal interface is further configured to fixthe device to the first terminal.
 3. The device of claim 2, wherein theterminal interface comprises a threaded cavity.
 4. The device of claim1, wherein the heat exchanger comprises at least one fin radiatingaround the first terminal.
 5. The device of claim 1, wherein the heatexchanger has a sufficiently high thermal performance that the energystorage cell requires terminal cooling only.
 6. The device of claim 5,wherein the energy storage cell has a second terminal; and, wherein thethermal performance of the heat exchanger is sufficiently high that thedevice may provide at least half of the terminal cooling of the energystorage cell.
 7. The device of claim 1, wherein the heat exchanger doesnot extend beyond the perimeter of the energy storage cell as viewedperpendicular to the first terminal.
 8. The device of claim 1, whereinthe heat exchanger comprises a plurality of round fins.
 9. The device ofclaim 1, further comprising a tool interface configured to couple to aninstallation/removal tool.
 10. The device of claim 9, wherein the toolinterface comprises a recessed tool interface.
 11. The device of claim1, wherein the terminal interface is further configured to fix anelectrical bridging device to the first terminal.
 12. The device ofclaim 11, further comprising a tool interface configured to couple to aninstallation/removal tool; wherein the terminal interface comprises athreaded cavity; wherein the heat exchanger comprises a plurality ofcircular fins, the fins not extending beyond the perimeter of the energystorage cell, as viewed perpendicular to the first terminal; and,wherein the terminal interface comprises a surface configured to pressthe electrical bridging device against the energy storage cell as thedevice is screwed on.
 13. A system for cooling a plurality of energystorage cells in a hybrid electric vehicle, the plurality of energystorage cells configured to store propulsion energy of the hybridelectric vehicle, each of the plurality of energy storage cells having afirst terminal, the system comprising: a plurality of terminal coolingdevices, each having a terminal interface configured to mechanically andthermally couple the terminal cooling device to the first terminal ofone of the plurality of energy storage cells, each terminal coolingdevice also having a heat exchanger configured to convectively transferheat away from the first terminal of its respective coupled energystorage cell; and, a coolant flowing across each of the heat exchangers.14. The system of claim 13, wherein each terminal interface comprises athreaded cavity and is configured to fix each terminal cooling device tothe first terminal of its respective coupled energy storage cell. 15.The system of claim 13, wherein each heat exchanger comprises at leastone fin radiating from the first terminal of its respective coupledenergy storage cell.
 16. The system of claim 13, wherein each heatexchanger has a sufficiently high thermal performance that itsrespective coupled energy storage cell requires terminal cooling only.17 The system of claim 16, wherein each of plurality of energy storagecells has a second terminal, the system further comprising wherein thethermal performance of the each heat exchanger is sufficiently high thateach of the plurality of terminal cooling devices may provide at leasthalf of the terminal cooling of its respective coupled energy storagecell.
 18. The system of claim 13, wherein each heat exchanger does notextend beyond the perimeter of its respective coupled energy storagecell as viewed perpendicular to the first terminal.
 19. The system ofclaim 13, wherein one of the plurality of terminal cooling devices isfurther configured to fix one end of an electrical bridging device to afirst energy storage cell; and, wherein another of the plurality ofterminal cooling devices is further configured to fix another end of theelectrical bridging device to a second energy storage cell.
 20. Thesystem of claim 19, wherein the plurality of terminal cooling deviceseach further comprise a tool interface configured to couple to aninstallation/removal tool; wherein the terminal interface of each of theplurality of terminal cooling devices comprises a threaded cavity, andfurther comprises a surface configured to press the electrical bridgingdevice against the energy storage cell as the device is screwed on; and,wherein the heat exchanger of each of the plurality of terminal coolingdevices comprises a plurality of circular fins, the fins not extendingbeyond the perimeter of the energy storage cell, as viewed perpendicularto the first terminal.
 21. A method for cooling a plurality ofultracapacitors in a hybrid electric vehicle, the plurality ofultracapacitors configured to store propulsion energy of the hybridelectric vehicle, each of the plurality of ultracapacitors having afirst terminal, the method comprising: providing a plurality of terminalcooling devices, each terminal cooling device having a terminalinterface and a heat exchanger; mechanically and thermally coupling eachterminal cooling device to the first terminal of one of the plurality ofultracapacitors respectively; providing a coolant flow across each ofthe terminal cooling devices; and, convecting heat away from theplurality of terminal cooling devices.